The FISA warrant application was largely based on a report by Christopher Steele. He may or may not have been described in the application as having a track record for reliability. But Steele himself witnessed nothing; he was relating hearsay from his "contacts," and it seems reasonable sure that the application did not describe each contact and show they have proven themselves reliable. If so, and the application did not state support for the claims, then it didn't meet the Fourth Amendment standard of probable cause. Which would mean the FISA court overlooked this, or issued it anyway, and so did the Deputy Attorney General, the head of the FBI, and everyone else in the chain of command. Which is hardly supportive of the idea that the present system has sufficient safeguards for privacy.

You are assuming the FISA warrant was based predominately on the Steele dossier. If you read the Nunes memo closely, you'll note that the Nunes memo does not claim the Steele dossier was the only or main or even significant evidence supporting the warrant application. We don't know what evidence the application used as support.

I can see those standards being required for a criminal warrant, but FISA warrants are different, are they not? As I recall, you can't really prosecute someone criminally based on the information you glean from monitoring through a FISA warrant because it's generally accepted that it would violate the Fourth Amendment rights of the accused.

This is why the DEA's Special Operations Division exists: To hide from the courts the ultimate (and unconstitutional) source of information used to criminally prosecute people through the use of things like "parallel construction" and falsely claiming an "anonymous tip".

Which of course, we should all be upset about, and perhaps the FISA court needs a complete revamping. Since they were created in the 1970's, they've approved nearly 40,000 FISA warrants, only rejecting 51 applications, an approval rate of about 99.87% That's pretty much the definition of a "rubber stamp" body right there.